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Comparison of the diffusive flame structure for Dodecane and OMEX fuels for conditions of Spray A of the ECN.
ISSN: 0148-7191, e-ISSN: 2688-3627
To be published on September 15, 2020 by SAE International in United States
A comparison of the flame structure for two different fuels, dodecane and oxymethylene dimethyl ether (OMEX), has been performed under condition of Spray A of the Engine Combustion Network (ECN). The experiments were carried out in a constant pressure vessel with wide optical access, at high pressure and temperature and controlled oxygen concentration. The flame structure analysis has been performed by measuring the formaldehyde and OH-radical distributions using Planar Laser-Induced Fluorescence (PLIF) techniques. To complement the analysis, this information was combined with that obtained with high speed imaging of natural luminosity and OH chemiluminescence radiation in the UV. Formaldehyde molecule is excited with the 355nm radiation from the third harmonic of a ND:YAG laser, whilst OH is excited with 281 nm wavelength from a dye laser. In both cases, the beam was transformed into a laser sheet in order to obtain a good spatial resolution of the flame and fluorescence was collected with an intensified camera (ICCD) and proper filtering. Consequently, two-dimensional maps in the flame axial plane were obtained at different instants after the start of ignition (SOI). Signal from both formaldehyde and OH chemical species can be compared, in order to analyse spatial distribution and interaction. Besides, the signal intensity can be related with each molecule concentration. In fuels with more oxygen atoms, such as OMEX, it has been possible to appreciate a more intense signal of both species, indicating that fuel oxidation takes place closer to stoichiometric conditions. This leads to lower amount of soot formation during combustion.